The subject matter of the present invention relates to a locking apparatus for a wellbore packer, and more particularly, to an apparatus adapted to be disposed in a wellbore for locking a setting apparatus to a mandrel, preventing any longitudinal movement of the setting apparatus relative to the mandrel, and preventing a packer connected to the mandrel from being set until a predetermined annulus pressure exists in the annulus section of the wellbore. When the predetermined annulus pressure is reached, the locking apparatus releases the mandrel from the setting apparatus thereby allowing the mandrel to move longitudinally relative to the setting apparatus. Since the packer is connected to the mandrel, any longitudinal movement of the mandrel relative to the setting apparatus will either set or unset the packer depending upon the direction of the longitudinal movement of the mandrel.
When a packer is lowered to a desired depth in a wellbore, it is initially placed in a safety position so that the packer will not set prematurely during its descent into the wellbore. In order to set the packer, it must first be removed from or taken out of its safety position. In order to remove the packer from its safety position, prior art packer setting apparatus required a user to first move a tubing string upwardly and then rotate the tubing string or to move the string up and down without rotation. Such movement of the tubing string can cause disruption of the depth correlation of the packer, as well as other tools, in the wellbore. Furthermore, such movement of the tubing string may accidentally set the packer. For example, since an upward movement followed by a rotational movement of a tubing string would set a prior art packer, the up and down motion of a drilling rig platform may provide the required movement of the tubing string which is necessary to accidentally set the packer. In addition, in deviated or horizontal boreholes, it was often necessary to rotate the tool string many times in order to generate a quarter turn at the packer, the quarter turn being required in order to take the packer out of the safety position. This can cause entanglement of hydraulic hoses used downhole. Accordingly, a new apparatus is needed to lock the packer in a safety position and to easily remove or unlock the packer from its safety position prior to setting the packer. Furthermore, once the packer is unlocked from its safety position downhole and set, any subsequent movement designed to unset the packer will cause the packer setting and unsetting apparatus to revert to standard operation.